1. Field of the Invention
The invention generally relates to a semiconductor device and method of manufacture and, more particularly, to a semiconductor device that includes strained silicon on a SiGe on a silicon-on-insulator substrate.
2. Background Description
Various techniques have emerged to improve performance of state of the art semiconductors. One technique involves introducing strain. Strained silicon exhibits improved semiconductor performance due to enhanced transport properties. Biaxial distortion of the crystal lattice in strained silicon improves electron and hole mobility.
Another performance enhancement technique involves providing a semiconductor layer separated from the substrate by an insulating layer. Also known as silicon-on-insulator (SOI), such structures exhibit reduced parasitic capacitance, thereby enabling a semiconductor to function at significantly higher speeds with reduced electrical losses. The result is an appreciable increase in performance and a reduction in power consumption.
By combining strained silicon with SOI the substantial benefits of both technologies may be realized. Unfortunately, however, current methods for forming strained silicon on SOI suffer drawbacks. One such method, the SIMOX method entails implantation of very high doses of oxygen ions at high energy. Upon annealing, the oxygen forms an oxide layer under the surface of the semiconductor. A problem with SIMOX is that it is relatively costly procedure. Another problem is that the high SIMOX annealing temperature (1350° C.) limits the concentration of germanium in SiGe-on-insulator substrates. For wafer bonding, which is another method, there are several technical hurdles including optimization of chemical mechanical polish, bonding conditions and the reduction in dislocation density.
The invention is directed to overcoming one or more of the problems as set forth above.